What SANS 791 covers
SANS 791 is the South African National Standard for uPVC sewer and drain pipe: underground, non-pressure pipe for sewage and storm water that flows by gravity. Our sewer and drain pipe is SATAS-certified to it (certificate SATAS 408.3/1).
It is made in two grades: heavy duty (HD) and normal duty (ND). The difference is the wall: HD is thicker, so it carries more load.
HD and ND compared, size by size
| SIZE (OD) | HEAVY DUTY | NORMAL DUTY | HD HEAVIER BY | LENGTH |
|---|---|---|---|---|
| 110 mm | 3.0 mm9.4 kg | 2.2 mm7.0 kg | 34% | 6 m |
| 160 mm | 4.7 mm21.5 kg | 3.2 mm14.8 kg | 45% | 6 m |
| 200 mm | 5.9 mm33.8 kg | 3.9 mm22.6 kg | 50% | 6 m |
| 250 mm | 7.3 mm52.4 kg | 5.0 mm36.2 kg | 45% | 6 m |
| 315 mm | 9.2 mm83.6 kg | 6.2 mm56.9 kg | 47% | 6 m |
| 355 mm | 10.2 mm101.4 kg | 7.0 mm70.2 kg | 44% | 5.8 m |
| 400 mm | 11.7 mm131.3 kg | 7.9 mm89.5 kg | 47% | 5.8 m |
| 450 mm | 13.2 mm167.0 kg | 8.8 mm112.5 kg | 48% | 5.8 m |
| 500 mm | 14.6 mm206.1 kg | 9.8 mm139.7 kg | 48% | 5.8 m |
Each cell: minimum wall thickness, then mass per pipe. Minimum wall thickness and mass per pipe. Pipe lengths are effective lengths, excluding the socket.
HD pipe is roughly a third to a half heavier than ND of the same size, because of its thicker wall.
How the grade is chosen
The design engineer specifies the grade from the conditions the pipe will be buried in:
- Depth: deeper trenches put more soil load on the pipe.
- Surface loads: pipe under roads, driveways or yards carries traffic loads as well as soil.
- Ground and bedding: how well the pipe is supported by the material around it.
As a general rule, HD goes where depth or loading is higher and ND where they're standard. Follow the drawing: the grade on it was chosen for that trench.
Laying sewer pipe well
- Lay on even bedding free of stones, so the pipe is supported along its length.
- Keep the design fall: gravity drainage needs a continuous slope with no sags.
- Lubricate the spigot and push it fully into the socket; the rubber seal is fitted at the factory.
- Backfill in layers around the pipe as the specification sets out before any heavy compaction above it.
Colour, lengths and joints
Our sewer pipe is cream, so it's easy to tell apart from blue pressure pipe on site. It comes in 6 m effective lengths up to 315 mm and 5.8 m from 355 to 500 mm, each with a socket and factory-fitted rubber seal.
Sewer and drain pipe is non-pressure pipe. For pumped sewage rising mains, use uPVC or mPVC pressure pipe.